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AOBPreview originally published online on April 27, 2005
Annals of Botany 2005 96(1):109-115; doi:10.1093/aob/mci156
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© The Author 2005. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oupjournals.org

Hardening by Partial Dehydration and ABA Increase Desiccation Tolerance in the Cyanobacterial Lichen Peltigera polydactylon

RICHARD P. BECKETT1, NOSISA MAYABA1, FARIDA V. MINIBAYEVA2,* and ALEXANDER J. ALYABYEV2

1 School of Botany and Zoology, University of KwaZulu-Natal, Private Bag X01, Scottsville 3209, Republic of South Africa and 2 Institute of Biochemistry and Biophysics, Russian Academy of Science, PO Box 30, Kazan 420111, Russia

* For correspondence. E-mail minibayeva{at}mail.knc.ru

Received: 3 December 2004    Returned for revision: 2 February 2005    Accepted: 9 March 2005    Published electronically: 27 April 2005

• Background and Aims The ability of partial dehydration and abscisic acid pretreatments to increase desiccation tolerance in the cyanobacterial lichen Peltigera polydactylon was tested.

• Methods Net photosynthesis and respiration were measured using infrared gas analysis during a drying and rehydration cycle. At the same time, the efficiency of photosystem two was measured using chlorophyll fluorescence, and the concentrations of chlorophyll a were spectrophotometrically assayed. Heat production was also measured during a shorter drying and rehydration cycle using differential dark microcalorimetry.

• Key Results Pretreating lichens by dehydrating them to a relative water content of approx. 0·65 for 3 d, followed by storing thalli hydrated for 1 d in the light, significantly improved their ability to recover net photosynthesis during rehydration after desiccation for 15 but not 30 d. Abscisic acid pretreatment could substitute for partial dehydration. The improved rates of photosynthesis during the rehydration of pretreated material were not accompanied by preservation of photosystem two activity or chlorophyll a concentrations compared with untreated lichens. Partial dehydration and ABA pretreatments appeared to have little direct effect on the desiccation tolerance of the mycobiont, because the bursts of respiration and heat production that occurred during rehydration were similar in control and pretreated lichens.

• Conclusions Results indicate that the photobiont of P. polydactylon possesses inducible tolerance mechanisms that reduce desiccation-induced damage to carbon fixation, and will therefore improve the supply of carbohydrates to the whole thallus following stress. In this lichen, ABA is involved in signal transduction pathways that increase tolerance of the photobiont.

Key words: Lichens, desiccation tolerance, abscisic acid, photosynthesis, chlorophyll, PSII activity, respiration, heat production


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